Related detection of multi-gas detectors
Gas is one of the four fundamental states of matter (the other three being solid, liquid, and plasma). Gases can be composed of individual atoms (such as rare gases), elemental molecules composed of one element (such as oxygen), compound molecules composed of multiple elements (such as carbon dioxide), and so on.
Gas mixtures can include various gaseous substances, such as air. The significant difference between gases, liquids, and solids is the large spacing between gas particles. This spacing makes it difficult for the human eye to detect colorless gases.
Gas, like liquid, is a fluid: it can flow and deform. Unlike liquids, gases can be compressed.
If there are no restrictions (such as containers or force fields), gases can diffuse without being limited in volume or fixed. The atoms or molecules of gaseous substances can move freely with each other.
The characteristics of gas are between liquid and plasma, and the temperature of gas will not exceed that of plasma. The lower limit of gas temperature is degenerate quark gas, which is increasingly being valued.
High density atomic gases cooled to very low temperatures can be classified into Bose gases and Fermi gases based on their statistical properties, while other phase states can refer to the phase state list.
Under standard conditions, the chemical elements that are gas molecules include hydrogen (H2), nitrogen (N2), oxygen (O2), and two halogens, fluorine (F2) and chlorine (Cl2), respectively.
In addition, there are rare single atom gases such as helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).
Because most gases are difficult to observe directly, they are often described by their four physical or macroscopic properties:
Pressure, volume, number of particles (expressed in moles by chemists), and temperature. These four attributes have been repeatedly observed by many scientists (such as Robert Boyle, Jacques Charles, John Dalton, Joseph Louis Gay Lussac, Amadeo Avogadro, etc.) through different gases and devices. Their careful study ultimately formed the ideal gas law that describes the mathematical relationships between these properties.
